Telegraph reperforator switching system



March 17, 1953 G. G. LIGHT TELEGRAPH REPERFORATOR swITcHING SYSTEM IAAIIIII INVENTOR G. G. LIGHT BY g ATTORNEY March 17, 1953 G. G. LIGHT TELEGRAPH REPERFORATOR SWITCHING SYSTEM l2 Sheets-Sheet 2 Filed July 8, 1946 M .O L OFI.

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BY ATTORNEY March 17, 1953 G, G, lGHT 2,632,044

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INVENTOR G. G. LGHT Evy/YW m .mv-L OP lli ATTORNEY March 17, 1953 G. G. LIGHT TELEGRAPH REPERFORATOR SWITCHING SYSTEM l2 Sheets-Sheet 7 Filed July 8 1946 lNvEN-roR G. G. lGHT BY/f'. W

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March 17, 1953 G. G. LIGHT' TELEGRAPH REPERFORATOR swITcHING SYSTEM 12 Sheets-Sheet lO Filed July a, 194e INVENTOR G. G. L.|GHT BY M ATTORNEY 8 m. F O T m ozL To FIG. |a

oo E VEm March 17, 1953 l G, G, LIGHT 2,632,044

TELEGRAPH REPERFORATOR SWITCHING SYSTEM Filed July 8, 1946 12 sheets-sheet 11 To FIG. |2

INVENTOR G. G. LIGHT ATTORNEY G. G. LIGHT TELEGRAPH REPERF'ORATOR SWITCHING SYSTEM March 17, 1953 12 Sheets-Sheet .l2

Filed July 8, 1946 INVENToR G. @LIGHT ATTORNEY Patented Mar. 17, 1953 UNITED STATES ATENT OFFICE TELEGRAPH REPERFORATOR SWITCHING SYSTEM 36 Claims. 1

This invention relates to telegraph systems and particularly to telegraph switching systems employing reperforator storing and repeating equipment.

In general terms, the object of this invention is to provide an improved telegraph reperforator switching system whereby telegraph messages may be more expeditiously and economically relayed through a telegraph switching oiiice or relaying station.

In a number of reperforator switching systems proposed. heretofore, such as for example the system described in the patent to Wheeler et al. No. 2,193,810, granted March 19, 1940, manually selective switching arrangements including plugs and jacks are employed to enable receivingT circuits to he extended to desired sending circuits. In systems of the Wheeler et al. type, all receiving circuits terminating at a switching ofiice have associated therewith code signal storage devices which operate to store the signals received at the switching oiiice in perforated tapes* The perforated tapes control associated tape transmitters and the output circuit of the transmitters terminates in a plug. In the operation of such a system the attendant, after noting the destination of a message in a storage tape, by means oi the plug and the proper jack. connects the transmitter to the desired outgoing or sending circuit. If

the outgoing circuit is idle at this time, transmission thereto begins, whereas if the circuit happens to he busy, transmission thereof is delayed until the circuit does become idle. After one message is completely transmitted to the outgoing circuit, the transmitter is automatically stopped by circuits controlled by an end-of-message signal in the storage tape and the attendant may then remove the plug from the jack preparatory to another plugging up operation in accordance with the destination of the next message stored in the storage tape. In such a system it is obvious that to eiect the switching or relaying of a message through a switching center, the attendant has two distinct operations to perform: inserting the plug into the jack assigned to the proper outgoing circuit, and after the transmission of the complete message, the removal of the plug from the jack. It is a feature of the present invention to provide manually operable selective switching circuits and equipment including push buttons and rotary switches in place oi plugs and jacks adapted to operate selectively and in such a manner that a minimum of time and effort of the attendant is required to relay a message through the switching center.

In the proposed system the attendant on observing the destination of the message in the storage tape operates a push hutten assigned to the desired outgoing circuit and at the completion of the transmission of the message to the outgoing circuit, the restoration of the circuits to their normal condition is automatic and requires no effort on the part of the attendant whatsoever. Since an attendant in the system disclosed herein has fewer duties to perform for the switching of a message through the switching center, other things being equal, the attendant can perform more switching operations in a given time.

A feature of the invention resides in the em,- ployment ci a plurality of rotary switches in such a manner that the number of connections avaliable to a tape transmitter, or the number of sending circuits to which a transmitter may be connected, is increased to some multiple of the number of connections capable of being established. 'oy a single rotary switch.

It often happens that some of the incoming circuits at a switching center are at times very heavily loaded in that the messages received thereover follow one another without any appreciable time interval separating the same. In such cases even though the selective switching equipment may require but a short interval of time to complete its function after the operator has noted the destination of the message, these delays are accumulative and may cause a number of untransmitted messages to be stored in the storage tape or the lousy receiving circuit and as long as the circuit remains busy, these messages continue to accumulate. To eliminate this possibility, the present invention employs a so-called alternator which operates in such a manner that the incoming circuit at the end of messages is shifted baci; and forth between two reperforator mechanisms and thus enables the storage of messages from a single receiving circuit in two storage tapes. With this arrangement the two storage tapes will have alternate messages therein. While a receiving circuit may be operating at its full capacity with. the above pointed out disadvantage of causing the accumulation of messages in a storage tape at the central oiiice, such a circuit may not be as heavily loaded during other periods. Accordingly, a three-position. control switch for the alternator is provided whereby the operation of the switch into any one of three positions causes the messages received. over the associated receiving circuit to al1 be stored in one storage tape or the other, or to be stored alternately in both storage tapes.

To facilitate the tracing of messages relayed through a reperforator switching center, each message as it is transmitted over a sending circuit usually has a service number and certain other information automatically appended thereto by means of an automatic message numbering machine of the type disclosed in the patent to Dirkes et al. No. 2,193,89, granted March 19, 1940. In the system disclosed herein there is provided one or more printing devices at the switching center which will print the numbers appended to the outgoing messages along with a part, such as the first line of the messages which include the originating point and destination thereof. These so-called monitoring printers which function to automatically record the rst line of each message relayed through or transmitted from the switching center are arranged in a so-called concentrator arrangement in such a manner that if the first monitor printer assigned to a group of lines is recording the first line of a message, the next printer will record the rst line of a second message switched through the center during the recording operation at the nrst monitor printer. With this arrangement the first monitor printer will record the first lines of all messages switched during idle periods thereof, and the capacity of the switching center' is not limited to the speed of operation of the monitor printers.

Still another feature of this invention resides in the provision of an improved and simplified arrangement and circuits for reading the characters as they are transmitted through a switching circuit for effecting the desired controls, such as the stopping of further transmission from a transmitter following the transmission of an end-of-message signal. In this respect the reading arrangement herein disclosed employs but two relays instead of the usual ve and the tape transmitter employed in conjunction therewith is arranged so that the contacts thereof do not interrupt -electric currents which thereby effects reduction in contact deterioration of the transmitter.

Other advantages and features of the invention will appear hereinafter in the following description of one embodiment thereof shown in the accompanying drawings wherein:

Fig. 1 is a diagrammatic view of the general arrangement of a system embodying the present invention;

Figs. 2 and 3 are detailed circuit diagrams of the alternator arrangement embodied in the invention;

Figs. 4, 5, 6, 7 and 8 are detailed circuit diagrams of the manually operative selective switching means of one repeating circuit included in the system;

Figs. 9 and 10 are circuit diagrams of a sending circuit;

Figs. 11 and 12 are circuit diagrams of a numbering machine distributor circuit; and

Fig. 13 is a diagram showing how Figs. 2 to 12, inclusive, may be arranged to form a complete circuit diagram of a receiving and a sending circuit as embodied in a system comprising the present invention.

General description Referring rst to Fig. 1, two branch oices BOI and BOZ are shown connected to the central oflice by means of receiving circuits RI, R2. As shown, theI receiving circuit R2 terminates in a printer perforator PPI, which responds to the signals received over the receiving circuit and stores such signals in a tape T. In the preferred embodiment of the invention, the printer perforator PPI prints characters representing the received signals on the tape T as well as perforating the tape in accordance therewith, and may be of the type disclosed in the patent to Dirkes et al. No. 2,174,731, granted October 3, 1939. The storage tape T prepared by the printer perforator PPI, passes to and controls a tape transmitter TTI which operates to cause signals corresponding to the characters stored in the tape to be transmitted over a sending circuit when connection to a sending circuit is established.

To establish connection from the transmitter to the desired sending circuit, a plurality of push buttons and rotary switches are employed. In the embodiment of the invention described herein, the push buttons are grouped into groups of twenty-five each with each group being arranged to operatively control an associated rotary switch. The two groups of push buttons associated with the tape transmitter TTI are identified as PBI and PB2 and have associated rotary switches RSI and RSZ, respectively. The points of the rotary switches RSI and RSZ are connected to the sending circuits extending from the central oflice and are identified as LI to L50. By operating a push button of the groups PBI and PB2 the tape transmitter TTI is connected to the sending circuit assigned to the operated push button and transmission of the message stored in the tape T will be initiated automatically if the selected sending circuit is idle or as soon as it becomes idle if it should be busy at the time of operation of the push button.

When there are no other messages received on the printer perforator PPI within a predetermined period following the end-of-message signal of a received message, a tape feed-out arrangement TFO automatically causes a sufficient length of tape T to be fed out of the printer perforator to permit the last message character to reach the sensing pins of the tape transmitter.

The receiving circuit RI terminates at the central office in an alternator ALT which has a manually operable switch associated therewith whereby the alternator functions to direct the messages received over RI alternately to printer perforators PPZ and PPS or to direct all messages to either one of the two printer perforators. Printer perforators PPZ and PP3 prepare tapes T for associated transmitters TT2 and TTS each of which have groups of push bottoms and rotary switches arranged in substantially the same manner as those associated with tape transmitter TTI.

The points of the rotary switches RSI and RSZ associated with tape transmitters TT2 and TT3 are connected in multiple with each other and with the points of the rotary switches associated with transmitter TTI so that the operation of the appropriate push button of any group connects the associated transmitter to the desired sending circuit LI to L50.

Numbering machines NMI, NM25, etc., are connected to each of the sending circuits LI to L25. etc. and operate to transmit over their respective sending circuits message numbers accompanying each message. Also connected to the sending circuits are the points of rotary switches RS3 and RS4. These rotary switches are so arranged that when a connection is made from a tape transmitter TT to a sending circuit L, the rotary switches also connect to such a line,

through concentrators CCI and CC2, one of a group of monitor printers such as thoseidentied as PTR. As long as a monitor printer is connected to a sending circuit L it will record or copy the signals sent over the sending circuit and the copied signals will include those sent from a message numbering machine such as NMI. Besides the message number, the monitor printers are adapted to also copy the rst line of each message. Since the point of origin and the address of a message are included in the rst line thereof, this information, together with the signals from the numbering machines give a readily available printed record of each switching operation. After copying the rst line of a message, the connected monitor printer is released to permit connection thereof to another sending circuit. The concentrators CCI and CC2 function in the usual manner to connect the lowest numbered idle monitor printer PTR to a sending circuit when a connection is established thereto. The number of monitor printers PTR associated with a concentrator such as CCI is governed by the traffic density over a group of lines such as LI to L25 to which the concentrator may be applied.

Alternator The so-called alternator operates to connect two printer-perforators alternately to a receiving circuit whereby these printer-perforators receive alternate messages. A manually operable switch included in the alternator circuit is effective to disable the same and thereby permit either one or the other of the two printer-perforators to be selected to receive all messages. As shown in Fig. 2 the receiving circuit RI, with a transfer relay 20| in a deenergized condition, extends through contacts 202 to the selecting magnet 203 of the printer-perforator 204. printer-perforator 204 is shown diagrammatically and may be of any suitable type such as, for example, that shown in Patent 2,174,731, granted October 3, 1939, to R. F. Dirkes et al., or Patent 2,143,828, granted January 10, 1939, to R. F'.

Dirkes et al. The rst of these patents discloses a combination telegraph printer and perforater adapted for use with start-stop signals while the latter discloses a similar instrument arrangedfor use with multiplex signals. Since the system as l described herein is arranged for use in a startstop system, the instrument covered by Patent 2,174,731 is best adapted for use in the present system.

The printer-perforator 204 includes a plurality V of selectively operable sets of contacts which may be Operated in accordance with the disclosure of Patent 2,143,328 and includes sets identified as' PH, and US. The CR contacts include individual sets 20.6 and 207 and are adapted to close when the CR or carriage return signal is received on the printer-perforator. The PH or punch hammer contacts including individual contact sets 263, 20S and 2 I0, are normally open and are momentarily closed by ymeans of a suitable link operated by the punch hammer which is actuated once during each cycle of operation of the printer-perforator. The US or unshift contacts are normally closed and open during receipt of a letters combination.

In the present system each message is terminated by an end-of-Inessage signal which cornprises two carriage return combinations followed by a letters combination. It is the end-of-message signal which in the manner described here-y The inafter operates the transfer relay 20| to transfer the receiving circuit RI from the printer-perorator 20d to printer-perforator 304 when the manually operable switch. 30| is in its mid-position. Similarly if the printer-perforator 304 is connected to the receiving circuit Ri, the end-ofmessage signal following a message received on this printer-perforator eiects release of transfer relay 20| to transfer the receiving circuit back to printer-perforator 204.

With the transfer relay 20| in its released position the receipt of a carriage return combination will close contacts 206 on the printer-perforator 22e. The closure of these contacts completes a circuit from ground through the lower contacts 302, which are closed with the switch 30| in its mid-position, the back contact and third left hand tongue of transfer relay 20|, a tongue and back contact of relay 2| I, the coil of relay 385 and a back Contact and tongue of relay 355 to battery. This circuit causes energization of relay 303 and contacts 202 of the punch hammer set, which will also be closed at this time, apply ground through the back contact and outer right hand tongue of relay 20|, the outer left hand tongue and back contact of a relay ZIS, the right hand tongue and back contact of relay 2I| to the tongue of relay 300 which is permanently grounded through the left hand coil of relay 2| I. With relay 300 at this time energized, the above grounded circuits are extended through the coil of this relay to battery, but as long as contacts 289 remain closed, relay 2 I I remains deenergized by virtue of the short-circuiting ground through contacts 2tlg. However, as soon as contacts 209 open at the end of this cycle of operation of the printer-perforator 204 to remove the short-circuiting ground, relay 2| I will become energized and this relay, together with relay 300, will be locked up by a circuit through the coils thereof; Thus in response to the rst carriage return character of an end-of-message signal, relays 2| I and 30G are energized and locked up.

If the next received character` on the printerperforator 2M is any character other than a carriage return, only the contacts operated by the punched hammer will be closed. In this event, the closure of contacts 209 establishes a circuit from ground through the back contact and outer right-hand tongue of relay 20|, the outer left-hand tongue and back contact of relay 2I3, the right-hand tongue, front contact and lefthand coil of relay 2i I, and through the coil of relay 305 to potential. This circuit causes the energization of relay 305 which in turn opens the locking circuit through the coils of relays 300 and 2H whereupon said relays release. The release of these relays returns the associated circuits to their normal condition or the condition they were in prior to the receipt cf the first carriage return.

If the character immediately following the rst carriage return is another carriage return, the second closure of contacts 20S establishes acircuit. for the energization of reiay 255. This circuit extends, as described, to the third left-hand tongue of relay 20| and thence via the left-hand tongues and front contacts of relay 2| I, the second left-hand tongue and back contact of relay 225 and through the coil of this relay to potential. When relay 20| is operated by the above circuit, it locks up by a circuit including its coil and i'lrst left-hand tongue and front Contact and a back contact or" a relay 2|i. The inner left-hand tongue of relay 20| is arranged in the well known manner to engage its front contact when the relay is energized and operates before the other tongues leave their back contacts.

The operation of relay through its two outer left-hand tongues and contacts 202 and 2 I 1 transfers the receiving circuit RI from the selecting magnet 203 of the printer-perforator 204 to the selecting magnet 303 of the printer-perforator 304. Concomitantly these tongues and contacts remove the holding potential 2|8 from the coil of the selecting magnet 303 of printer-perforator 304 and apply it to the selecting magnet 203 of printer-perforator 204.

The closure of the punch hammer contacts 209 concomitantly with the closure of contacts 206 in response to the second carriage return effects release of relays 2| and 300 in the manner described.

The first carriage return of the end-of-message signal of the next message which will be received on printer-perforator 304 will cause energization of relay 300 since the operation of relay 20| transfers the operating circuit for this relay to contacts 306 of printer perforator 304. The operation of relay 20| also transfers the circuit from punch hammer contacts 208 of printer perforator 204 to punch hammer contacts 308 of printer perforator 304. Thus, the counting and control relays of the alternator circuit count carriage return signals in substantially the same manner when either one of the printer perforators is connected to the receiving circuit. The second closure of contacts 306, with relay 2|| operated, establishes a circuit through the inner left-hand tongue and front contact of relay 2|| through the coil of relay 2|9 to potential at the inner right-hand tongue and front Contact of relay 20| whereby relay 2 9 is energized. Simultaneously with the energization of relay 2|9 the closure of contacts 309 establishes a circuit for the energization of relay 305. Energization of relay 305 through its right-hand tongue places a short-circuiting ground around the coil of relay 2|3 in parallel with the ground from the carriage return contacts 306. Thus, as long as contacts 306 and 309 remain closed the operation of relay 2| 9 will not cause energization of relay 2 |3. However, when contacts 306 and 309 open, the short-circuiting grounds around the coil of relay 2|3 are removed and the said relay will become energized by a circuit extending from ground through the coil thereof, the front contact, tongue and coil of relay 2|9, to potential at the front contact and inner right-hand tongue of relay 20|.

Operation of relay 2|3 through its right-hand tongue completes a circuit for the energization of relay 26 which in operating opens the locking circuit of relay 20| which thereupon releases and restores the circuits controlled thereby to their previous condition with the receiving circuit extending to the selecting magnet 203 of printer perforator 204.

Since the transfer from one printer perforator to the other is effected soon after the receipt of the second carriage return of an end-of-message signal, the actual transfer of the receiving circuit may occur during the receipt of the accompanying letters character. However, the nature of the letters character is such that the partial receipt thereof, on either of the printer perforators will not adversely affect their operation or the operation of the associated control circuits.

The alternator operates in the above described manner to switch successive messages alternately to the printer perforators 204 and 304 with the switch 30| in its midposition. The switch 30| in either of its other two operative positions is effective to disable the alternator circuits and prevent the automatic switching from one printer perforator to the other at the end of a message. If, for example, the receiving circuit Rl is extended to the printer perforator 204, as will be the case when the transfer relay 20| is deenergized, the operation of key switch 30| to such a position as to open the contacts 302 thereof prevents further end-of-message signals from causing operation of the transfer relay 20| and the receiving circuit will therefore remain connected to the selecting magnet 203 of printer perforator 204. Similarly, if the transfer relay 20| happens to be energized, in which condition the receiving circuit is extended to the selecting magnet 303 of printer perforator 304, the operation of key switch 30| to such a position as to open normally closed contacts 3|| prevents the end-of-rnessage signal from causing the transfer of the receiving circuit back to the printerperforator 204. Thus by operating the key switch 30|, either one of the printer perforators 204 or 304, which happen to be connected to the receiving circuit, may be selected to remain connected to the circuit or the key switch 30| may be operated so that the transfer will occur at the end of the message being received. In this case the transfer will be to the idle printer-perforator and this printer perforator will receive all following messages.

Tape fcedout control In the preferred arrangement of the system each printer perforator, whether it be one of a pair such as 204 and 304 or one such as PPI, Fig. l, adapted to receive all the messages incoming over a receiving circuit, has tape feedout circuits associated therewith. The tape feedout arrangement is effective to cause the printer perforator to meter out tape at the end of a received message or after the receipt of the end-of-message signal provided a taut tape condition exists between the printer perforator and its associated tape transmitter. The actual circuits for tape feedout control for printer perforators 204 and 304 are shown in Figs. 2 and 3 and that associated with printer-perforator 204 will now be described.

The purpose of the tape feedout control is to automatically feed out sufficient tape from the printer perforator to enable the last perforated character of the received message to be advanced sufciently to reach the sensing pins of the associated tape transmitter. The tape feedout employs contacts 201 of the carriage return set, contacts 208 and 2li] of the punch hammer set, together with the normally closed unshift contacts 22|, all of which are on each printerperforator. Since the unshift contacts 22| are normally closed, an obvious circuit is normally established to maintain relay 222 in an energized condition. The receipt of the rst carriage return of an end-of-message signal completes a circuit through contacts 20'! and 208 and the left-hand coil of a relay 223 and a resistance 224 to positive potential. Relay 223 thereupon operates and locks up through a circuit including its inner left-hand tongue. Simultaneously with the completion of the circuit through the lefthand coil of relay 223 and the energization thereof, the closure of contacts 2|0 completes a circuit through the right hand tongue and right hand coil of relay 223 and resistance 226 to positive potential. The right and left hand coils of relay 223 are arranged in opposition but the relay does not release on completion of the circuits through the two coils thereof in as much as resistance 22e is of higher value than resistance 224, permitting a higher current to flow through the left-hand winding. The operation of relay 223 completes a circuit from ground through the front contact and outer left-hand tongue thereof, the front contact and left-hand tongue of relay 222, through the coil of a relay 227i and resistances 228 and 222 to potential at the tongue and front contact of the selecting magnet 2933. The above circuit causes relay 22? to operate, which through its tongue and front contact locks up independently of the contacts of relays 222 and 223. The locking circuit for relay 22T is from ground through a resistance 23! to th* tongue of said relay.

Thus, in response to a carriage return signal, relays 222, 223 and 22T will be in an energized condition. On the receipt of the second carriage return of an end-of-message signal, the position of the relays are not changed. However, if either one of the carriage return signals is followed by l some character other than a letters character or another carriage return, the relays are released. During receipt of such a character the closure oi contacts 2 l i? of the punch hammer set completes a circuit from ground through the right-hand tongue and front contact of relay 222, the righthand tongue and front contact o relay 223, and resistance 225 to positive potential. 'Ihe iiow of current through the right-hand coil of relay 223 is in opposite direction to the flow through the left-hand coil and the value of resistances 22@ and 232 in the locking circuit through the lefthand coil is greater than the value of resistance 226 and hence the greater now of current in the right-hand coil will cause relay 223 to release. As relay 223 releases, ground is applied through contacts 233 to one side of the coil of a relay 232. This prevents operation of relay 23d should the tape lever controlled by the tape 235 issuing from the printer-perforator 224 happen to be closed at this time. The operation of the tape lever contacts will be described hereinafter.

When a letters character directly Afollows the two carriage return characters as is the case at the end of a message, the operation of the unshit contacts 22! opens the circuit through relay 222 which releases and in turn opens the circuit through the right-hand coil of relay 223. However, relays 223 and 22l remain energized as the locking circuits thereto are not disturbed. Should the two carriage return signals be followed by more than one letters character, the momentary closing of contacts 22i will cause corresponding energizations of relay 222. Relay 222 in operating will cause reenergization of relay 22T which is released on the start pulse of each character. In this case the characters will be letters, the start pulses of which open the locking circuit to relay 221 at the front contact of the selecting magnet 223. However, since relay 222 causes reenergization of relay 22?, the final condition of relay 221 is energized after the receipt of one or more letters characters.

With relay 221 energized, the condition is established for the operation of relay 234 contingent upon the position of the tape lever il, Fig. 4, controlled by the tape 235. When the tape 236 is not taut, tape lever controlled contacts 402 will be in an open condition, and as the transmitter $03 operates to advance the tape 236 therethrough to reduce the amount of tape between the printer-perforator and the transmitter, the tape lever itl causes contacts i362 to close. Closing of contacts 402 by a condition of taut tape applies ground over conductor iM to complete a circuit through the coil of relay 23d to the tongue of relay 22? and thence over the above described circuit to potential at the front contact of the selecting magnet 2i3. This circuit causes energization of relay 23d whereupon its left-hand tongue short-circuits the coil of relay 227 whereupon said relay releases. The release of relay 22'! in turn causes release of relay 234. However, the operation of relay 23d before its release completes a circuit from ground at its outer righthand tongue, through the coil of a tape feedout control magnet 2.3i to potential whereby said magnet is energized to initiate a tape feedout operation by the printer-perforator 204. The tape feedout control mechanism initiated into a cycle of operation by energization of magnet 231 may be any of the well known types.

rIhe release of relays 234 and 22T in the manner described prevents a subsequent tape eedout operation until after another message has been received by the printer-perforator 2M and the tape feedout mechanism of the printer-perforator is so arranged that should another message be received during a tape feedout operation, the tape feedout operation will be interrupted and the tape 23's perforated in accordance with received signals. In as much as the tape feedout is initiated in response to a letters character, the selection of which remains set up in the printerperforator, the tape issuing from the printerperiorator during the tape feedout operation will be perforated with letters characters.

A selective switching circuit is included in the equipment which enables a message stored in a tape, such as tape 23B, to be switched to and transmitted over the desired sending circuit. Such equipment is normally provided for each receiving position or each printer-perforator that may store messages in an associated tape. Primarily the equipment of each selective switching circuit includes a tape transmitter, a distributor transmitter, one or more multi-level rotary switches and a like number of groups of push buttons or selecting keys, signal lamps and control relays. Figs. 4 to 8, inclusive, show the details of one such selective switching circuit wherein two rotary switches are employed'with two associated groups of controlling push buttons.

The sending circuits over which the stored messages are transmitted terminate on the points of one of the levels of the rotary switches of a selective switching circuit and these points are connected in multiple to corresponding points of the rotary switches of all other selective switching circuits. Assigned to each such point in each selecting circuit is an individual push button, and since it is impractical for obvious reasons to construct a rotary switch with greater than a given number of points, for example, twenty-rive points, one such rotary switch is required for each such group of twenty-uve stations to which messages may be switched.

The tape transmitter with its associated distributor transmitter is connectable to the wipers of the rotary switches or its associated selective switching circuit, and the depression of any particular push button will cause the tape transmitter and distributor transmitter to be connected through the wipers to the points on the rotary switch associated with the depressed push button.

Thus a message in the tape of any tape transmitter may be directed to any of the outgoing circuits by depressing the proper push button of the selective switching circuit associated with that particular tape transmitter.

In the description of the selective switching circuit shown in the drawings, Figs. 4 to 8, it will be assumed that this circuit is associated with the printer-perforator 204, Fig. 2, and that the tape 236 issuing from the printer-perforator 204 is arranged to control the tape transmitter 403 of this circuit. It will also be assumed that the conductor 404 from the tape lever contacts 462 extends to one terminal of the coil of relay 234. It will be understood that each of the other printer-perforators, such as 304, Fig. 3, and PPI, Fig. 1, has associated therewith similar selective switching circuits.

As described above in connection with the tape feedout circuit, successive messages in a tape are separated by end-of-message signals and if a succeeding message does not follow immediately, sufficient letters chara-cters are perforated in the tape to permit the last intelligence character of a message to be advanced over the pins of the transmitter. Accordingly, in the idle condition of a printer-perforator and assuming there is no message in the tape between a printer-perforator and its associated tape transmitter, the tape between these two units will be taut and consist exclusively of letters perforations. In order that the first character of a message subsequently received on the printer-perforator may reach the pins of the tape transmitter, the selective switching circuit is arranged on slack tape conditions to idle through the transmitter all such letter perforations separating messages. These letter perforations consist of all ve intelligence impulses thereof being of marking polarity and the manner in which the selective switching circuit herein disclosed is arranged to idle such letters characters through the transmitter and detect the first character of the subsequent message constitutes one of the novel features of the present invention.

The tape transmitter 403 may be of any suitable type found in the prior art such as, for example, the tape transmitter disclosed in Patent No. 2,172,269, granted September 5, 1939, to H. Angle et al. The transmitter 403 consists essentially of a set of ve tongues which are positioned in accordance with the perforations in the control tape 236 to engage either the marking or spacing contacts. When the sensing pin of the transmitter senses a perforation in the tape the tongue engages its marking contact whereas in sensing a non-perforated section in the tape, the tongue engages its spacing contact. A stepping magnet SM periodically energized during the operation of the transmitter advances the tape therethrough. In the circuit about to be described, the five tongues of the transmitter are connected by individual conductors to one terminal of associated contacts I to 5 of a distributor transmitter 406, the other terminals of which are grounded. Also included in the distributor are contacts 6, 'I and 8, and during the idle or normal condition of the distributor, contacts I to 5 and I to 9 are open and lcontact 6 closed as shown. The distributor 406 also has a clutch magnet CM which when energized in a manner to be described operates a clutch to release a rotatable member for rotation, and during the rotation thereof it actuates the contacts I to 8 in a predetermined mannel.

The spacing contacts of the tape transmitter 403 are connected, in the manner shown, through back contacts and left-hand tongues of a relay 401 and the coil of relay 408 to potential. Accordingly, as long as the tongues of transmitter 403 remain out of engagement with their spacing contacts, and relay 401 remains deenergized, relay 408 will also remain deenergized. Since the letters combinations in the tape 236 have all marking signaling conditions, relay 408 will remain deenergized as long as such characters appear over the pins of the transmitter 403 or the transmitter remains in an idle condition.

If it is assumed that the tape 236 is taut and has nothing but letters characters therein and that the printer-perforator 204 begins to receive another message and store the same in tape 236, the extra supply of tape will enlarge the tape loop and the tape lever 40| will allow contacts 409 to close. The closure of contacts 409 for the assumed condition completes a circuit to the clutch magnet CM of the distributor 406 and this circuit rnay be traced from ground through a key 4II, a tongue and back contact of relay 408, a back contact and right-hand tongue of relay 401, contacts 400, conductor 4I2, a back contact and tongue of a relay 50|, conductor 502 and through the coil of clutch magnet CM to potential. The clutch magnet will thereupon release the distributor 406 for continuous operation which will continue until the clutch magnet circuit is interrupted. During each cycle of operation of the distributor 406 the closure of contacts No. 8 thereof completes a circuit for the energization of the stepping magnet SM of the transmitter 403. This circuit extends from ground at contact No. 8 over conductor 4I3, a left-hand tongue and back contact of a relay 10|, conductor 102, the outer righthand tongue and back contact of relay 408 and through the coil of stepping magnet SM to potential. This periodical energization of the stepping magnet SM will effect advancement of the tape 236 with the letters perforations therein through the transmitter 403.

When the rst character of the message in the tape reaches the pins of the transmitter 403, one or more of the tongues thereof will engage associated spacing contacts. During the following cycle of operation of the distributor 406 in applying ground to the tongues of transmitter 403 a circuit will be completed for the energization of relay 408. When relay 408 thus operates it will be locked up through a circuit including the inner left-hand tongue and back contact of relay 401, the front contact and second left-hand tongue of relay 408 and key 4I I. The operation of relay 408 opens the described circuits to the clutch magnet CM of the distributor 406 and the stepping magnet of the tape transmitter 403. In addition, the operation of relay 408 through its inner right-hand tongue applies ground over conductor 4I4 to the terminal of relay 60I that has battery connected thereto. This short-circuits the coil of slow-to-release relay 60I whereupon said relay, which is normally energized, releases. The opening of the circuit to the clutch magnet CM causes the distributor to come to rest at the end of its current cycle of operation while the interruption of the circuit to the stepping magnet SM prevents the first intelligence character of the message from being advanced out of operative relationship with the pins of the transmitter 403. Another function performed by the energization of relay 408 is the completion of a circuit to the message waiting lamp 602. The latter circuit extends from potential at the lamp 602, through the left-hand tongue and back contact of relay i503, conductor 6045, the inner left-hand tongue and front contact of relay 498, conductor 4I6, the upper tongue and back contact of relay 80|, conductor 7M, to ground at the back contact and lower tongue of the relay 103. The operator, by means of the illumination of the message Waiting lamp SEZ, is appraised that a message or at least its rst part is stored in the tape 236 and is waiting to be switched through the system. The operator thereupon inspects the tape to determine from the printed portion thereof the destination of the message and depresses the proper push button of this selective switching circuit.

As shown in t'igs, '7 and 8, the push buttons are arranged in groups with the rectangle 'it including push buttons l to 25 inclusive, and rectangle Slifi including push buttons numbered 2t to U, inclusive. Each group of push buttons 196 and 866 has associated 'therewith a multiple level rotary switch 'lill and 851, respectively. The push buttons are divided into groups of 25 with each provided with an associated rotary switch because of the physical limitations of providing a rotary switch with more than 25 points thereon and to reduce the maximum number of steps that a rotary switch will be required to take to pick up the desired sending circuit. The present system is shown and described as including but two groups each of 25 push buttons with their associated rotary switches which provides for a maximum of 50 sending circuits. It will be apparent, however, that the push buttons may be arranged in a single group or in groups of less or more than 25 each, and that additional groups may be added to a system when it is desired to provide for more sending circuits.

Each of the keys in a group, such as 'ict and BUS, have the upper terminals thereof connected over individual conductors to corresponding points on the fth or upper levels of associated rotary switches lill' and Sill, respectively. In Fig. '7 these connections for keys l and 25 only are shown, it being understood that corresponding contacts or the remaining switches are similarly connected. The movable element of each push button is normally in engagement with the upper contact thereof and the movable elements of the push buttons of both groups are connected in multiple to conductor lh which in the idle condition of the selective switching circuit is grounded through the second righthand tongue and back contact of relay lili. Thus, in the idle condition of the circuit all the points of the upper levels of rotary switches "itil and Sill are grounded.

The lower elements of the push buttons in group liit are connected in multiple to a circuit extending through the lefthand coil of a relay '88 to potential at the back contact and innerleft-hand tongue of a relay 2&3. In a similar manner the lower elements of the push buttons in group Stil are connected in multiple to a circuit extending through the left-hand coil of relay 808 to potential at the inner left-hand tongue and back. contact of relay ltd.

The operation of a push button removes ground from its associated point on the rst level of its rotary switch and, if it is assumed that a push button in group ltd is operated. push button No. l, for example, its operation will remove the ground from the iirst point of the upper level oi rotary switch lill and complete a circuit through the key for the operation of relay W8. The circuit for the operation of relay 'NJB is contingent upon relay SGS being in a deenerg'ized condition in the same manner that the operation of relay s, in response to the actuation of one of the push buttons 2E to 5G of group `8th-is contingent upon relay 'H38 being ina deenergized condition. rihus the relays 108 and 868 are controlled in such a manner that only either one or the other but not both can be operated at a time.

The operation of either one of the relays 108 or 8138 completes a circuit for the energization of the step magnet SM of the rotary switch associated with the operated one of the push buttons. If it is assumed that push button No. I of group W6 is operated, relay "Hi8 will be energized and through its right-hand tongue completes a circuit frcm battery through the associated rotary switch step magnet SM, the interrupter contacts 'HI thereof, the right-hand tongue and front contact of relay 108, the upper tongue and back contact of relay 'm3 to the wiper of the upper level of rotary switch ll. Since al1 the points on the upper level of rotary switch lill with the exception of the one connected to the actuated push button will at this time be grounded through the contacts of their respective push buttons, the step magnet SM will self-step until the upper wiper finds the ungrounded or No. l point, and when the upper wiper reaches this point, further operation of the rotary switch will cease. Relay m3 will thereupon become energized since at this time the shunt circuit to ground around the coil of said relay '83 and the right-hand coil of relay ltd is interrupted. The operating circuit for relay 'lt is grounded at the outer right-hand tongue and bach contact of relay lili and although this circuit includes the coil of the step magnet SM of rotary switch lill, the current flow is insufficient to operate said step magnet.

The operation of relay 'ifi establishes connections through front contacts and tongues thereof, to the wipers of the first, second, third and fourth levels of switch lill and through its lower tongue interrupts the described circuit to the message waiting lamp 652. If the circuit corresponding to the actuated push button is, at this time, available or idle the corresponding point on the rst level of the rotary switch lill will have ground applied thereto by conductor l I4 and since the wiper will at this time be in contact with this point, the grounded circuit will be extended through the wiper, a tongue and front contact of relay i133, conductor H3, the fourth right-hand tongue and back contact of relay te? and the filament of a standby lamp M5 to potential. The illumination of the standby lamp M5 indicates to the operator that the switching function has been completed.

The operation of relay its in extending the circuit from the wiper of the third level of rotary switch it? completes a circuit from conductor 55 connected to the first point of this level to conductor 'H8 to the middle tongue of a relay 818. Since relay 848 is at this time deenergized, the said circuit is not extended further. Similarly, conductor 'H6 connected to the point on which the second wiper of switch 101 is at this time resting, is extended through a front contact and tongue of relay les, conductor H9, to a tongue of relay till that has its associated front contact connected to the normally closed No. 6 contacts of distributor dat. At the same time conductor lll, connected to the corresponding point of the fourth level of switch lill, is extended through the front contact and tongue of relay 183, conductor 12i, the coil of relay S |78, conductor 8|9, the back contact and tongue of relay 60| to one of the points on an interrupter 605. The interrupter 60G includes a constantly rotating brush arm 601 which progressively contacts associated points, each one of which is individually associated with selective switching circuits such as that disclosed herein. The circuit to the brush arm `601 extends through normally closed contacts 608 of key 609 and the back contact and tongue of a relay 6|I to ground. The conductors 1|4, 1|5, 1|6 and 1|1 are respectively referred to hereinafter as the lamp circuit, the clutch circuit, the line circuit, and the seize circuit. Conductor 1|4, as will be described, extends at this time to ground while conductors 1|5 and 1|6 are at this time open, and conductor 1|1 extends to positive potential through a resistance. The other points of the first four levels of rotary switch 101 and those of rotary switch 801 extend in a similar manner to corresponding terminals of associated sending circuits,

If the sending circuit to which the message has been directed is idle at the time relay 103 is operated or when it does become idle, the seize circuit 1|1 will be conditioned to effect operation of relay 8|8 when the interrupter wiper 601 contacts the point thereon assigned to calling selective switching circuit. The resistance in this circuit in the arrangement hereinafter described prevents operation of relay 8|8 if another selective switching circuit is connected to the desired sending circuit and the interrupter 606 is so arranged to permit only one switching circuit to be connected to the desired sending circuit should two or more such switching circuits be waiting for connection thereto. Thus in accordance with the above, relay 8|8 will only be operated when the desired sending circuit is idle.

The operation of relay 8|8 completes a circuit for the operation of relay 401 which circuit may be traced from potential through the coil of said relay 401, conductor 4|1 to ground at the front contact and outer tongue of relay 8|8. Relay 8|8 in operating locks up by a circuit from ground through the inner right-hand tongue and back contact of relay 10|, to the front contact and inner tongue of relay 8|8 and the coil thereof to potential over the described circuit. The operation of relay 8|8 through its center tongue extends the clutch circuit (conductor 1|5) over conductor 82| to the front contact associated with the tongue of relay 401 in the described circuit to the clutch magnet CM of distributor 406. Since relay 401 will at this time be energized and conductor 1|5 is at this time open at the sending circuit, the clutch controlled by the magnet CM will not for the time being be released. As relay 401 operated it locked up through its inner right hand tongue and conductor 420 to ground at the front contact and outer left-hand tongue of relay 108.

The completion of the circuit to the clutch magnet CM of the distributor 406 conditions the selective switching circuit to transmit signals representative of the message stored in the storage tape 236. However, transmission of the message does not start immediately since certain other signals are transmitted over the sending circuit ahead of the message. These extra signals include the message number which is transmitted automatically in a manner to be described. For this reason the sending circuit will not be connected at this time to conductor 1|6 and, therefore, for the time being conductors 1|5 and 1 I6 will remain open. After the automatic transmission of the message number, conductor 1|! is grounded and conductor 1| 6 is extended to the sending circuit selected by the operated push button whereupon the distributor 406 operates to transmit the signals stored in the tape to the sending circuit.

Relay 401 which was operated in the manner described above as the result of operation of relay 8|8 establishes a circuit for reading the end-ofmessage signal appended to each message in the tape 236. Relay 401 in operating also interrupts the locking circuit through its inner left-hand tongue to relay 408 whereupon said relay releases. A further function effected by the energization of relay 401 through its fourth right-hand tongue is the extinguishing of the standby lamp 4|5 and lighting of a connected lamp 4|9. This advises the operator that the switching circuit has been connected to the sending circuit and that transmission of the message stored in the tape will begin as soon as the automatic message number is transmitted. Relay 42| included in the selective switching circuit is arranged therein in such a manner as to cause the operation of another relay 422 when the first, second, third and fifth pulses of a character are spacing as determined by the position of the pins of the tape transmitter 463. Since the first. second, third and fth pulses of a carriage return character are spacing, relay 422 will be operated only on a carriage return character 0r on a blank character. In the case of a blank character the fourth impulse of the character over the pins will be spacing and relay 422 will be released by virtue of a circuit from the No. 4 contact of the distributor transmitter 406 through the opposing or left-hand coil of relay 422.

When a carriage return character is stepped over the pins of the tape transmitter 403, the closure of No. l contacts of distributor transmitter 406, on the associated cycle of operation, applies ground through the rst tongue and spacing contact of the tape transmitter, the outer left-hand tongue and front contact of relay 401 to potential through the left-hand coil of relay 42|. This circuit effects operation of relay 42| and it is held operated during the closure of the No. 2 contacts from distributor 406 by a circuit including the second tongue and spacing contact of the tape transmitter 403 and the inner lefthand tongue and front contact of relay 42|. Thus, relay 42| is operated and held operated during the transmission of the rst two spacing impulses of a character, and if the third and fth impulses are also spacing, as will be the case in a carriage return character, relay 42| continues to be held operated by a circuit from ground at the distributor 406 through the No. 3 contacts thereof, the third tongue and spacing contact of transmitter 403, the spacing contact and No. 5 tongue of transmitter 403, the righthand tongue, front contact and right-hand coil of relay 42 conductor 423, the back contact and outer left-hand tongue of a relay 504, conductor 506, and the right-hand coil of relay 422 to potential which also effects operation of relay 422. Contacts No. 1 on the distributor 406 are arranged to close at the middle of the fourth impulse transmitted therefrom and open at the end of the fifth impulse. During the transmission of a carriage return character, relay 422 will be energized, as described, and the accompanying closure of the No. 1 contacts of distributor 406 completes a circuit from ground thereat over conductor 424, through a tongue and back contact 

